Several publications show cellular shades, wherein a fabric material is formed to define parallel tubular cells extending horizontally across the width of the shade. Air within each of the cells only circulates minimally, such that when expanded the shade provides good thermal insulation.
It is, of course, desirable to make the physical appearance of the shade as attractive as possible. Similarly, it is desirable to make such shades as economically as possible, which requires both that a minimal amount of material be used to form each cell and that the manufacturing process be as expeditious as possible.
Various exemplary prior art disclosures include the following:
Netherlands patent application No. 6706563 to Landa discloses a screen wherein a plurality of strips of a fabric material are folded about fold lines extending longitudinally and bonded together, the two edges of each strip being bonded to the center of the next successive strip, to form a screen consisting of a plurality of tubular cells. The Landa screen is intended to be used such that the cells extend vertically.
U.S. Pat. No. 4,347,887 to Brown shows a "thermal shutter". A wide band of material is folded transversely to form a double column of adjacent cells, which may have rounded visible contours. The cells are adhesively bonded to one another. The Brown structure is symmetrical, so that both sides of the shade thus formed have essentially the same appearance.
U.S. Pat. No. 4,450,027 to Colson shows a method and apparatus for fabricating a multiple cell shade wherein a continuous relatively narrow strip of fabric is folded longitudinally in order to define pleats in the shade material and the edges folded over on the center portion to create a tubular cell. Successive cells are assembled by applying an adhesive to folded over edges of the cells, and adhering each cell to the preceding cell when wound on a stacking rack.
U.S. Pat. No. 4,631,217 to Anderson shows in FIG. 3 a shade of asymmetrical construction. A rear wall section of each cell is essentially straight or linear when the shade is in its expanded position. The width of these rear wall sections thus defines the spacing of the adjacent cells, while the front of each cell, containing more material, presents a pleated outward appearance.
The Anderson patent also discloses a method of forming an expandable and collapsible shade consisting of an assembly of horizontally parallel cells, in which the cell structure is formed from a material folded into a Z-shape rather than from a U-shape as shown in the Colson patent.
U.S. Pat. No. 4,846,243 to Schneider shows a foldable window covering formed of a wide material folded transversely, as in the Brown patent, to yield a collapsible shade. The front surface of the shade consists of a number of drooping loops formed by doubling the material back on itself. The successive cells are spaced in the expanded position of the shade by a relatively vertical rear wall section of each cell.
Roman shades are often preferred by consumers for their smooth and uncreased but drooping appearance to the room interior. While the disclosures cited above provide shades which may be commercially producible in relatively high volume, only Schneider shows a Roman shade type shade. However, the Schneider shade is formed of a wide strip of material folded transversely, which limits the width of the shade which can be formed to the width of the stock material available. Also, the application of adhesive lines in the transverse direction on fabrics is problematic in that straight lines are difficult to achieve. A significant drawback to traditional Roman shades is that they generally must be jobbed out to seamstresses and take significantly longer and often cost more to make than the various pleated shades disclosed above.